Reference is also made to my related applications Ser. No. 06/817,114, filed on Jan. 8, 1986, entitled Variable Color Digital Timepiece, now U.S. Pat. No. 4,647,217 issued on Mar. 3, 1987, Ser. No. 06/919,425, filed on Oct. 16, 1986, entitled Electronic Timepiece with Transducers, now U.S. Pat. No. 4,687,340 issued on Aug. 18, 1987, Ser. No. 06/926,511, filed on Nov. 3, 1986, entitled Electronic Timepiece with Physical Transducer, now U.S. Pat. No. 4,705,406 issued on Nov. 10, 1987, Ser. No. 07/150,913, filed on Feb. 1, 1988, entitled Variable Color Display Typewriter, now U.S. Pat. No. 4,824,269 issued on Apr. 25, 1989, Ser. No. 07/336,080, filed on Apr. 11, 1989, entitled Variable Color Display Typewriter, now U.S. Pat. No. 4,934,852 issued on Jun. 19, 1990, Ser. No. 06/839,526, filed on Mar. 14, 1986, entitled Variable Color Display Telephone, now U.S. Pat. No. 4,726,059 issued on Feb. 16, 1988, Ser. No. 06/940/100, filed on Dec. 10, 1986, entitled Digital Voltmeter with Variable Color Background, now U.S. Pat. No. 4,831,326 issued on May 16, 1989, Ser. No. 06/882,430, filed on Jul. 7, 1986, entitled Display Device with Variable Color Background, now U.S. Pat. No. 4,734,619 issued on Mar. 29, 1988, Ser. No. 07/518,779, filed on May 4, 1990, entitled Measuring Device with Variable Color Background, now U.S. Pat. No. 5,003,247 issued on Mar. 26, 1991, Ser. No. 07/528,229, filed on May 24, 1990, entitled Measuring Device with Variable Color Display, now U.S. Pat. No. 5,057,768 issued on Oct. 15, 1991, Ser. No. 08/422,090, filed on Mar. 31, 1995, entitled Digital Color Display System, now U.S. Pat. No. 5,561,365 issued on Oct. 1, 1996, Ser. No. 06/922,847, filed on Oct. 24, 1986, entitled Continuously Variable Color Display Device, now U.S. Pat. No. 4,845,481 issued on Jul. 4, 1989, Ser. No. 07/322,341, filed on Mar. 13, 1989, entitled Continuously Variable Color Optical Device, now U.S. Pat. No. 4,965,561 issued on Oct. 23, 1990, Ser. No. 07/379,616, filed on Jul. 14, 1989, entitled Variable Color Digital Display for Emphasizing Position of Decimal Point, now U.S. Pat. No. 5,003,298 issued on Mar. 26, 1991, Ser. No. 06/925,543, filed on Oct. 31, 1986, entitled Variable Color Complementary Display Device, now U.S. Pat. No. 4,804,890, issued on Feb. 14, 1989, Ser. No. 06/920,740, filed on Oct. 20, 1986, entitled Step Variable Color Display Device, now abandoned, Ser. No. 06/931,626, filed on Nov. 17, 1986, entitled Variable Color Hybrid Display Device, now abandoned, Ser. No. 07/157,603, filed on Feb. 19, 1988, entitled Variable Color Multiplexed Display System, now abandoned, and Ser. No. 07/000,478, filed on Jan. 5, 1987, entitled Variable Color Digital Tachometer, now abandoned, which describe the devices employing a variable color display.
1. Field of the Invention
This invention relates to a variable color complementary display device.
2. Description of the Prior Art
A display device described in U.S. Pat. No. 3,740,570, issued on Jun. 19, 1973 to George R. Kaelin et al., uses special LEDs that exhibit different colors when subjected to different currents. The LEDs are biased by pulses of different amplitudes, to achieve different colors of the display, and by the length inversely proportional to the pulse amplitude, to compensate for variable brightness of the display caused by different amplitudes of the pulses.
A circuit employing a dual-color LED driven by a dual timer is described in the article by Bill Wagner entitled 2-color LED+driver=versatile visual effects, published on Oct. 2, 1980 in EDN volume 25, No. 19, page 164. Since dual-color LEDs are connected to conduct currents in opposite directions, it would be impossible to forwardly bias them simultaneously.
A luminescent solid state status indicator is disclosed in U.S. Pat. No. 3,873,979 issued on Mar. 25, 1975 to Magnus G. Craford et al. The status indicator includes two light emitting diodes inverted in parallel, which may be of different colors or of the same color.
An electronic display having segments wherein each segment is capable of selectively illuminating two colors is disclosed in U.S. Pat. No. 4,488,149 issued on Dec. 11, 1984 to William A. Givens, Jr. Two AND gates are provided for biasing, in each display segment, either a first light emitting diode, for emitting a first color, or a second light emitting diode, for emitting a second color. It is not contemplated to illuminate both light emitting diodes in each segment simultaneously for blending the colors.
A multi-color LED display for seven segment figures is disclosed in German Patent No. 3,009,416 issued on Sep. 17, 1981 to Klaus Gillessen. The LED circuit consists of seven group of diodes, each group made up of two diodes, one red and one green. The cathodes of all red diodes are terminated in a common connection, and the green ones likewise, the anodes of each pair of diodes being common for that pair. Two transistors connected in cascade are utilized for activating either all green LEDs, or all red LEDs, but not both simultaneously. When a low level signal is applied to the base of the first transistor, the first transistor is blocked, and the second transistor is turned ON to illuminate the second set of the diodes. When a high level signal is applied to the input of the first transistor, the first transistor is turned ON, while the second transistor is blocked, whereby the first set of the diodes is illuminated. Since the first transistor cannot be simultaneously turned ON and OFF, it would be impossible to illuminate the two sets of the diodes simultaneously. In another embodiment is shown a multi-color LED display utilizing three sets of LEDs: red, green, and blue, which are respectively commonly. connected and may be activated by manual switches. It is not contemplated that the three sets of LEDs be activated in selective combinations to blend the colors.
A digital electrooptical display with anti-parallel light emitting diodes is disclosed in East German Patent No. 220,844 issued on Apr. 10, 1985 to Thomas Hoffmann et al. Two light emitting diodes for emitting light of different colors are connected in each segment back-to-back. Since the light emitting diodes are connected to conduct currents in opposite directions, it would be impossible to illuminate them simultaneously, because the opposite currents attempting to pass through a single conductor would cancel.
A method and apparatus for independent color control of alphanumeric display and background therefor are disclosed in U.S. Pat. No. 3,911,418, issued on Oct. 7, 1975 to Minoru Takeda. Two color control signals, for the foreground area and for the background area, are provided separately from a computer and are processed separately, by means of a foreground selector and background selector. The two color control signals are then merged at a CRT display in raster fashion.
An error detection for multi-segmented indicia display is disclosed in U.S. Pat. No. 4,301,450, issued on Nov. 17, 1981 to Gerald D. Smoliar. A contiguous xe2x80x9cOFFxe2x80x9d segment of one color is provided next to each xe2x80x9cONxe2x80x9d segment so as to indicate unambiguously that each non-illuminated xe2x80x9cONxe2x80x9d segment is in fact indicating xe2x80x9cOFFxe2x80x9d.
The prior art does not contemplate a variable color complementary display device using anti-parallel (back-to-back connected) light emitting diodes, on which a selective display unit may be exhibited in a desired color, by activating the display areas which correspond by their positions to the display unit, and on which the remaining display areas automatically illuminate in a complementary, or otherwise contrasting, color, without the need for conversion of the color control signals to complementary color control signals.
In a broad sense, it is the principal object of this invention to provide an improved variable color complementary display device.
It is another object of the invention to provide a variable color display device having improved readability of the exhibited display unit.
It is still another object of the invention to provide a variable color display device in which the display unit, exhibited in a selective color, is enhanced by a substantially complementary or otherwise contrasting color.
It is still another object of the invention to provide a variable color complementary display device for illuminating certain display areas in a selected color, and for automatically illuminating the remaining display areas in a color substantially complementary, without the need for converting the color control signals.
It is still another object of the invention to provide a variable color complementary display device using the pairs of anti-parallel (back-to-back connected) light emitting diodes of respective primary colors, the light emitting diodes in each pair being of the same color.
It is still another object of the invention to provide a variable color complementary display device including a decoder for developing output signals for illuminating the light emitting diodes in certain display areas in a display color, and for developing opposite output signals for illuminating the light emitting diodes in the remaining display areas in a complementary, or otherwise contrasting, color to the display color.
In summary, a variable color complementary display device of the invention includes a plurality of display areas arranged in a pattern for selectively exhibiting a plurality of display units. Each display area includes a plurality of pairs of light emitting diodes for emitting, when forwardly biased, light signals of respective primary colors and a device for combining the light signals in the display area to obtain a light signal of a composite color. Each pair includes a first light emitting diode and a second light emitting diode of the same color.
The invention resides in the anti-parallel connecting of the first light emitting diode and the second light emitting diode in each pair, such that their polarities are opposite. An activation device is provided for forwardly biasing the selective ones of the first light emitting diodes in the selected display areas, for illuminating them in a desired display color. As a result of the anti-parallel arrangement, a new and unexpected result is obtained: the second light emitting diodes in the remaining display areas are automatically illuminated in the remaining primary colors, resulting in a color which is substantially complementary to the display color. In the preferred embodiment, the activation device includes a decoder for developing active output signals, for selecting the display areas that correspond by their arrangement to the desired display unit, and for developing the opposite output signals, -for selecting the remaining display areas. The activation device further includes a plurality of buses, equal in number to the plurality of primary colors and respectively associated therewith, to which the first light emitting diodes are commonly coupled in accordance with their colors, for being forwardly biased when the respective bus is energized.